Acela carried more than 3.4 million passengers in fiscal year 2016; second only to the slower and less expensive Northeast Regional, which had over 8 million passengers in FY 2016. Its 2016 revenue of US$585 million was 25% of Amtrak's total.[1]

Acela operates along routes that are used by freight and slower regional passenger traffic, and only reaches the maximum allowed speed of the tracks along some sections, with the fastest peak speed along segments between Mansfield, Massachusetts and Richmond, Rhode Island. Acela trains use tilting technology, which helps control lateral centripetal forces, allowing the train to travel at higher speeds on the sharply curved NEC without disturbing passengers.[8] The high-speed operation occurs mostly along the 226-mile (364 km) route from Pennsylvania Station in New York City to Union Station in Washington, D.C., with a fastest scheduled time of 2 hours and 45 minutes and an average speed of 82.2 mph (132 km/h), including time spent at intermediate stops.[3][9] Over this route, Acela and the Northeast Regional service captured a 75% share of air/train commuters between New York and Washington in 2011, up from 37% in 2000.[10]

The Acela's speed is limited by traffic and infrastructure on the route's northern half. On the 231-mile (372 km) section from Boston's South Station to New York's Penn Station, the fastest scheduled time is 3 hours and 30 minutes, or an average speed of 66 mph (106 km/h).[2][11] Along this section, Acela has still captured a 54% share of the combined train and air market.[12][13] The entire 457-mile (735 km) route from Boston to Washington takes between 6 hours, 38 minutes and 6 hours, 50 minutes,[2] at an average of around 70.3 mph (113 km/h).[14]

The present Acela Express equipment will be replaced by new Avelia Liberty trainsets beginning in 2021. Amtrak will retire all current trains by the end of 2022.[15]

Amtrak asked railway equipment manufacturers to submit proposals. An X 2000 train was leased from Sweden for test runs from October 1992 to January 1993. It was operated from Washington, D.C. to New York City from February to May and August to September 1993. Siemens showed the ICE 1 train from Germany, organizing the ICE Train North America Tour which started to operate on the Northeast Corridor on July 3, 1993.[17] This testing allowed Amtrak to define a set of specifications that went into a public tender in October 1994.[18]

In October 1994, Amtrak requested bids from train manufacturers for a trainset that could reach 150 miles per hour (240 km/h).[18] A joint project of Bombardier (75%) and GEC Alsthom (now Alstom) (25%) was selected in March 1996.[18] An inaugural VIP run of the Acela occurred on November 16, 2000[23], with the VIP train being led by power car number 2020 with no. 2009 at the opposite end, followed by the first revenue run on December 11, 2000, a few months after the intended date.[24]

Then-Vice President Joe Biden and Senator Arlen Specter riding the Acela Express to Philadelphia in February 2009

By 2005, Amtrak's share of the common-carrier market between New York and Boston had reached 40%, from 18% pre-Acela.[25] With the increasing popularity of the faster, modern Acela Express, Metroliner service was phased out in late 2006.[26][27] To meet the demand, more Acela services were added in September 2005.[28] By August 2008 crowding had become noticeable.[29]

By 2011, the Acela fleet had reached half of its designed service life. Amtrak proposed several replacement options, including one as part of its A Vision for High-Speed Rail in the Northeast Corridor.[5] In 2011, Amtrak announced that forty new Acela coaches would be ordered in 2012 to increase capacity on existing trainsets. The existing trains would have received two more coaches, lengthening the trainsets from a 1-6-1 configuration to 1-8-1 (power car — passenger cars — power car). The longer trainsets would have required the modifications of the Acela maintenance facilities in Boston, New York and Washington. The first of the stretched trainsets was to have entered service in fiscal year 2014.[30] This plan was cancelled in 2012 in favor of replacing, rather than refurbishing, the Acela fleet.[31]

In January 2014, Amtrak issued a request for proposals on 28 or more new model Acela trainsets, in a combined order with the California High-Speed Rail Authority. These bids were due May 17, 2014.[32] After discussions with manufacturers, Amtrak and the California High Speed Rail Authority concluded their needs were too disparate for common rolling stock and decided not to pursue the joint option.[33]

Amtrak's original contract with the Bombardier-Alstom consortium was for the delivery of 20 trainsets (6 coaches each, with power cars at front and rear) for $800 million.[34] By 2004, Amtrak had settled contract disputes with the consortium, paying a total of $1.2 billion for the 20 trainsets plus 15 extra high-speed locomotives and the construction of maintenance facilities in Boston, New York, and Washington.[35]

The Acela name was announced on March 9, 1999, as a part of the original announcement of the service itself.[36] Amtrak originally intended for this move to be part of a rebranding of the majority of their Northeast services,[37] forming three levels: Acela Express, Acela Regional, and Acela Commuter.[38] The branding team based the name "Acela" on the ideas of acceleration and excellence.[39][40]

The Acela Regional name was first applied to NortheastDirect trains 130–133 on January 31, 2000.[41] Those trains, 130 and 131 running weekdays only and 132 and 133 running every day, were the first electrified trains to run on the full Northeast Corridor.[42] As more trains were electrified, they too were rebranded. In 2003, due to confusion between the lower-speed Acela Regional trains and the Acela Express, the Acela branding was removed from the NortheastDirect service (now the Northeast Regional) and the Acela Commuter had its name changed back to the Clocker for a similar reason; the Clocker was ultimately discontinued on October 28, 2005.[43]

Overhead view of an Acela power car in Boston; an MBTAOrange Line subway train is also visible in the background.

The first-generation Acela trainset is a unique set of vehicles designed specifically to satisfy governmental rolling stock requirements established primarily by the Federal Railroad Administration (FRA). This includes the ability to withstand a collision with a freight train at speed without collapsing. Most manufacturers which bid on the Acela were unable to meet the structural requirements, due to increased costs and complications for the manufacture of the trains, and the need for manufacturers to make significant engineering changes to their standard designs. In the end, only three qualified bidders remained: ABB (Swedish-Swiss manufacturer of the X 2000 train), Siemens (manufacturer of the German ICE), and a consortium of Bombardier (manufacturer of the LRC trains) and Alstom (manufacturer of the French TGV).[25]

The design, using identical 6,200 horsepower (4,600 kW) power cars at each end which operate on a voltage of 11,000 volts AC, and either 25 or 60 Hz frequency, derives several components from the TGV,[46] such as the third-generation TGV's traction system (including the four asynchronous AC motors per power car, rectifiers, inverters, and regenerative braking), the trucks/bogies structure (a long wheelbase dual transom H frame welded steel with outboard mounted tapered roller bearings), the brake discs (although there are only three per axle, versus four on the TGV), and crash energy management techniques to control structural deformation in the event of an accident.[45][46]

The tilting carriages are based upon Bombardier's earlier LRC trains used on Via Rail rather than the TGV's non-tilting articulated trailers. Acela power cars and passenger cars are much heavier than those of the TGV in order to meet the FRA's crash standards.[47] French and Canadian crews testing the Acela referred to it as "the fast pig" due to its weight.[48][49] The extra weight leads to the Acela's power-to-weight ratio being about 22.4 hp per tonne, compared to 30.8 hp for a SNCF TGV Reseau trainset.[46] The Tier II crash standards, adopted in 1999, have also resulted in the passenger cars being designed without steps and trapdoors, which means that the trainsets can only serve lines with high-level platforms such as the Northeast Corridor. Acela trains are semi-permanently coupled (but not articulated as in the TGV) and are referred to as trainsets. Bombardier later used the Acela carriage design and a diesel/gas turbine variant of the power car for its experimental JetTrain.[50]

With a 71:23 gear ratio, the Acela is designed with a top speed of 165 mph (266 km/h) and reaches a maximum speed of 150 mph (240 km/h) in regular service on three sections of track totaling 33.9 miles (55 km) in Rhode Island and Massachusetts.[7] The Acela achieves an average speed (including stops) of 82.2 mph (132.3 km/h) between Washington and New York,[3][9] and an average speed of 66 mph (106 km/h) from New York to Boston.[2][11] The average speed over the entire route is a slightly faster 70.3 mph (113 km/h).[2][14]

In practice, the Acela's speed depends more on local restrictions along its corridor than on its trainset. In addition to speed restrictions through urban areas, the Acela's corridor includes several speed restrictions below 60–80 mph (97–129 km/h) over older bridges, or through tunnels a century old or more. Altogether, Amtrak has identified 224 bridges along Acela's route that are beyond their design life.[51]

To prepare for the Acela launch, Amtrak upgraded the track along the Connecticut shoreline east of New Haven to allow maximum speeds in excess of 110 mph (177 km/h).[52] West of New York City, the Acela's top speed is 135 mph (217 km/h).[7] One limiting factor is the overhead catenary support system which was constructed before 1935 and lacks the constant-tension features of the new catenary east of New Haven.[5] The Pennsylvania Railroad ran Metroliner test trains in the late 1960s as fast as 164 mph (264 km/h) and briefly intended to run the Metroliner service at speeds reaching 150 mph (241 km/h). Certification testing for commercial operation at 160 mph (257 km/h) involving test runs at up to 165 mph (266 km/h) began between Trenton and New Brunswick in September 2012.[53]

The slowest section of the electrified NEC is the portion owned by Metro-North Railroad and the Connecticut Department of Transportation between New Haven, Connecticut and New Rochelle, New York and is heavily used by commuter trains. Amtrak's trains here achieve 90 mph (145 km/h) only on a limited 4 mi (6.4 km) stretch in New York State and rarely exceed 60 mph (97 km/h) at any time eastbound through Connecticut until reaching New Haven.[54] In 1992, ConnDOT began plans to upgrade the catenary system, replace outdated bridges, and straighten certain sections of the New Haven Line to enable the Acela to run slightly faster. Curve straightening was later deemed too expensive.[citation needed] As of May 2017[update] the catenary replacement and bridge work were under way and expected to be completed by mid-2018.[55]

On July 9, 2007, Amtrak introduced a limited-stop round trip, with trains stopping only at Philadelphia between New York and Washington. This shortened the trip between the two cities to 2 hours 35 minutes, making the trip roughly an hour faster than some of the Northeast Regional train services. These trains were an experiment to find ways to expedite travel time on the Acela; Amtrak has since dropped them.[56]

Acela Express's fastest schedule between New York and Washington, DC was 2 hours and 45 minutes in 2012. $450 million was allotted by President Barack Obama's administration to replace catenary and upgrade signals[57] between Trenton and New Brunswick, which will allow speeds of 160 mph (257 km/h) over a 23 mi (37 km) stretch. The improvements were scheduled to be completed in 2016, but have been delayed; the project is now scheduled to be finished in 2019.[58] This section of track holds the record for the highest speed by a train in the US, which is 170.8 mph (274.9 km/h), achieved in a test run by the U.S./Canada-built UAC TurboTrain on December 20, 1967.[5][59]

Tilting enables passengers to ride more comfortably on curved sections of track faster than would otherwise be possible, by leaning into the bend. Acela trainsets tilt above 60 mph (97 km/h) on most of the system, but some segments of track in the Northeast Corridor are too close together for the cars to safely tilt while maintaining FRA minimum space between trains on parallel tracks. Metro-North Railroad restricts tilting on the segment of track north of New York which it owns. The system was originally designed for a 6.8° tilt, but the cars were redesigned 4 in (100 mm) wider to accommodate wider seats and aisles that reduced allowable tilt to 4.2° to fit within the clearance constraints of the existing tracks.[45] Traveling at higher than 135 mph (217 km/h) also requires constant-tension catenary, which is only implemented on the more modern catenary system north of New York City. South of New York City, the trains are restricted to 135 mph (217 km/h). By comparison, the Northeast Regional and the now-defunct Metroliner service reached 125 mph (201 km/h).

Acela service was originally expected to begin in late 1999 but was delayed. The catenary system could not support the intended speeds between Washington DC and New York City, but the newer system between New York City and Boston allows the higher speeds. Attention was drawn to the decreased 4.2° tilt, but this was not the root of the speed problem, as the tracks from New York to Boston are similar to those between New York and Washington, and the tilt mechanism is not the factor enabling higher speeds.[18][45] Following repairs, the first Acela service began on December 11, 2000, a year behind schedule.[62]

Acela travels between Boston and New York in about three and a half hours (an improvement of half an hour); New York to Washington runs take a minimum two hours and forty-five minutes.[2] These schedules, as well as the relative convenience of direct downtown-to-downtown rail service as opposed to air travel, especially after the September 11 attacks, have made the Acela Express more competitive with the air shuttles. Due to this competition, Southwest Airlines canceled service between Washington and New York.[63]

Due to the high speed at which Acela trains bypass platforms of local stations, concerns have mounted in some communities over inadequate warnings and safeguards for passengers waiting for other trains, including that the two-foot wide yellow platform markings may not keep people at a safe distance. At Kingston station in Rhode Island and Mansfield station in Massachusetts, Acela trains pass by at 150 mph (241 km/h).[64][65] Suggestions include platform safety barriers, or use of different announcements for approaching Acela trains versus slower ones.[66] In 2011, federal transportation grants were awarded to improve Kingston station, including the construction of a third track to be used by the Acela as a through track to bypass the station, helping to alleviate safety concerns.[67] Renovations were officially completed on October 30, 2017.[68][69]

In August 2002, shortly after their introduction, Acela trainsets were briefly removed from service when the brackets that connected truck (bogie) dampers (shocks) to the powerunit carbodies ("yaw dampers") were found to be cracking.[70][71] The Acela returned to service when a program of frequent inspections was instituted. The damper brackets have since been redesigned and old brackets replaced by the newer design.

On April 15, 2005, the Acela was removed from service when cracks were found in the disc brakes of many passenger coaches.[72] The Bombardier-Alstom consortium replaced the discs under warranty. Limited service resumed in July 2005, as a portion of the fleet operated with new brake discs.[73]Metroliner trains, which the Acela Express was intended to replace, filled in during the outage. Amtrak announced on September 21, 2005, that all 20 trainsets had been returned to full operation.

The Acela Express trainset consists of two power cars, a café car, a First Class car, and four Business Class cars, semi-permanently coupled together. It has fewer seats than regional service counterparts. The First Class car has 44 seats, being three seats across (one on one side, two on the other side) and four seat tables. There are 260 Business Class seats on each trainset; these cars have four seats across (two on each side) and four-seat tables.[6][dead link] Reservations guarantee seating but seats are not assigned. Baggage may be stowed in overhead compartments or underneath seats. Trains are wheelchair-accessible. Cars have one or two toilets each, with one ADA compliant.

The car adjacent to First Class is designated as the quiet car, where passengers are asked to refrain from loud talking and phone conversations. Automatic sliding doors between cars reduce noise.

Generally Amtrak train crews consist of an engineer, a conductor, and at least one assistant conductor. Acela trains also have an On-Board Service crew consisting of two First Class attendants and a Cafe Car attendant. In addition to the food service provided in the Cafe Car, on most trains an attendant will also provide at seat cart service, serving refreshments throughout the train. First Class passengers are served meals at their seats on all services.[74]

At Amtrak, the On-Board Service crew is considered separate and subordinate to the Train and Engine crews. Acela maintenance is generally taken care of at the Ivy City facility in Washington, DC; Sunnyside Yard in Queens, New York; or Southampton Street Yard in Boston.

The Acela trainsets underwent minor refurbishments between mid-2009 and 2010 at Penn Coach Yard, next to 30th Street Station in Philadelphia, Pennsylvania. These refurbishments included new blue leather seats throughout the trainset.[75]

Wireless Internet station service began in 2004.[76] In 2010, with services provided by The GBS Group, all Acela trains began offering "AmtrakConnect" (SSID AmtrakConnectAcela) supporting IEEE 802.11​a/b/g/n, 2.4 GHz and 5 GHz and standard VPN connections.[77]

The first Acelagrade crossing accident occurred on September 27, 2005, when a car rolled under closed crossing gate arms in Waterford, Connecticut, and was struck by a train traveling at 70 miles per hour (110 km/h), killing three. None of the 130 passengers were injured. The gates were found to have been functioning properly,[79][80] but the incident drew much criticism regarding the eleven remaining grade crossings along Amtrak's busy Northeast Corridor.[81]

On March 24, 2017, an Acela Express train derailed at low speed in New York's Penn Station during morning rush hour. All 248 passengers were safely evacuated.[82] The derailment was caused by a defective section of track, of which Amtrak was aware, but had not yet fixed.[83]

On February 6, 2018, Acela Express train No. 2150 split apart between the first and second cars in the trainset at 124 mph. There were no injuries to the crew or the 52 passengers on board, who were transferred to Northeast Regional train No. 180.[84][85]

On August 26, 2016, Vice President Joe Biden announced a $2.45 billion federal loan package to pay for new Acela equipment, as well as upgrades to the NEC. The loans will finance 28 train-sets that will replace the existing fleet of twenty. This will allow for hourly New York-Boston service all day and half-hourly New York-Washington service at peak hours.[86] The new trains will be called Avelia Liberty. They will have 30% greater seating capacity, active tilt technology and could operate at 186 miles per hour (299 km/h) if infrastructure improvements were completed to allow the higher speeds. The trains will be built by Alstom in Hornell and Rochester, New York. The new trains will be phased in between 2021 and 2022, after which the current fleet is to be retired.[87] Amtrak will pay off the loans from increased NEC passenger revenue.

^Philips, Don (January 2010). "Now it seems to be official: Freight rail is the future". Trains. Vol. 70 no. 1. p. 10. When the train was being tested at the technology center in Pueblo, Colo., I had lunch one day out on the ballast with the French and Canadian crews doing the testing. The conversation turned to the weight of the Acela, which the crews considered laughably too heavy. At one point, a French engineer confided that the crews called the train "le cochon", meaning "the pig". The man and his supervisor immediately realized he had said too much. They asked me to keep that a secret, and I did for many years until I was sure everyone on the program had moved on to other jobs.

^Dao, James; Wald, Matthew L.; Phillips, Don; Dao (April 24, 2005). "Acela, Built to Be Rail's Savior, Bedevils Amtrak at Every Turn". The New York Times. Retrieved March 4, 2008. Before the first train was built, the Federal Railroad Administration required it to meet crash safety standards that senior Amtrak officials considered too strict. That forced the manufacturers, Bombardier Inc. of Canada and GEC Alstom of France, to make the trains twice as heavy as European models. Workers dubbed the trains le cochon -- the pig.

^"Metro-North Railroad EMPLOYEE TIMETABLE No. 4"(PDF). Metro-North Railroad. June 21, 2010 [February 5, 2006]. Archived from the original(PDF) on October 19, 2012. Retrieved December 29, 2013. This notes, on p.41, that the 90 mph section is from MP (mile post) 17.2 to MP 21.4; that begins midway between New Rochelle and Larchmont, and ends between Mamaroneck and Harrison.